| Element | Thallium | Symbol | Tl |
| Atomic Number | 81 | Molar Mass | 204.37 gmol-1 |
| Electron Configuration | [Xe]4f145d106s26p1 | Normal State | solid metal |
| Density @STP | 11.87 g cm-3 | Melting Point | 304oC |
| Boiling Point | 1473oC | Stable Isotopes | 201Tl, 203Tl |
| Atomic Radius | 171 pm | Ionic Radius | 88 (3+) pm |
| Electronegativity (Pauling) | 2.04 | Ionization Energy (1st) | 589 kJ mol-1 |
| Ionization Energy (2nd) | 1971 kJ mol-1 | Ionization Energy (3rd) | 2878 kJ mol-1 |
| Molar Heat Capacity | 26.3 J K-1mol-1 | Standard Molar Entropy | 64.2 J K-1mol-1 |
| Enthalpy of Fusion | 4.31 kJ mol-1 | Enthalpy of Vapourization | 162.1 kJ mol-1 |